The present invention relates to a method for producing a uniform, continuous band of fibers in which the deviation of the actual value of the quantity of fibers in the band from a given desired value is utilized to regulate the rate at which fibers are introduced into a carding machine.
In order to make the card sliver leaving the carding machine more uniform with respect to its cross-sectional shape, it is known to employ a comparison signal to vary the speed ratio between card input and card output at least one location, and thus to vary the dwell time within the carding machine. For this purpose, a meaasuring element furnishes a signal which is proportional to the cross section of the sliver. An amplified signal representative of long term fluctuations in such cross section acts on a regulatable drive so as to control the rate of rotation, for example of a feed roller in that it is decelerated when there is too much material and is accelerated when there is a deficiency of material. The feed roller receives the fiber material from a scrutcher lap, or beater.
One drawback of this method is that it requires complicated apparatus. A further drawback is that it is not always possible to arbitrarily change the rate of rotation of the machine parts which transport the fiber material. Since the card with all its parts is adjusted to a certain optimum mode of operation and deviations can be taberated only within very close limits, considerable difficulties may develop during processing.
In a known process disclosed in German Auslegeschrift (Published patent application) No. 1,510,302, a carding machine is associated with a measuring device which monitors the length of silver leaving the machine and being delivered to a roving can and acts to cause each can to be filled with a selected length of silver. After each can has been thus filled, it is weighed and whenever the measured weight falls outside of a desired weight range, the rate of delivery of fibers to the carding machine is subsequently altered in a direction to bring the weight of subsequently filled cans into the desired range.
Of course, this method entails long lapses of time between production of sliver with a weight outside of the desired range and effectuation of a correcting adjustment. Only one correction indication is produced for each silver length serving to fill a roving can. Fluctuations occurring during production of such a length of sliver can not be corrected and if the weight, or cross section, of a silver fluctuates, during the filling of a single can, about a value in the desired weight range, this will go entirely undetected even though silver portions of appreciable length may have sizes, i.e., weights per unit length, or cross sections, which deviate considerably from the desired range. In other words, it is perfectly possible, when practicing this known method, to produce a silver having substantial portions with an unacceptably large or small cross section without producing any indication that could serve to correct the condition.